Time cycle warp-stop motion control for weaving looms

ABSTRACT

A circuit is disclosed for controlling the energization of the solenoid for actuating the conventional power-stop motion of a weaving loom in the event either of power failure or of breakage of warp threads. A silicon-controlled rectifier (SCR) is connected in series with the solenoid and an AC voltage supply. Gating of the SCR is controlled by a unique transistor flip-flop circuit, the state of which is responsive to two different threshold voltages established at a control point. The voltage at the control point is determined by an RC charging and discharging circuit conditionally responsive to the drop wire contacts. The RC circuit is adjusted so that a definite charging time must elapse after the opening of the drop wire contacts until the flip-flop changes state to gate the SCR into conduction. This time is made longer than the time of a pick-cycle of the loom.

United States Patent.

[72] Inventors Harry P. Hansen 3,343,158 9/1967 Tellerman 66/163 UX Martinsville; 2,531,944 1 1/1950 Metcalf 139/353 WRITE" Barber Planfleld! boih 3,373,773 3/1968 Balentine, Jr. et al. 139/336 X NJ. 3,529,444 9/1970 Romoli 66/163 X l [2 1 P No Primary Examiner-James Kee Chi [22] Filed Feb. 13, 1970 A" M h J B dch A J [45] Patented Dec. 7, 1971 orneysars a reen an es er l iams, r. [73] Assignee The Singer Company New ABSTRACT: A circuit is disclosed for controlling the energization of the solenoid for actuating the conventional power- [54] TIME CYCLE WARFSTOP MOTION CONTROL :top motlonfof a Lveaving loom I: th:j event lelther of pen/e;

FOR WEAVING Looms allure or o brea age 0 warp t rea s. A s1 icon-contro e 7 Ciaims 1 Draw. Fl rectifier (SCR) lS connected in series with the solenoid and an g AC voltage supply. Gating of the SCR is controlled by a [52] US. Cl 139/336, unique transistor flip-flop circuit, the state of which is respon- 13 /1 sive to two different threshold voltages established at a control [51] Hut. Cl 003d 51/00 point. The voltage at the control point is determined by an RC Field of Search charging and discharging circuit conditionally responsive to 2 the drop wire contacts. The RC circuit is adjusted so that a definite charging time must elapse after the opening of the [56] defences cued drop wire contacts until the flip-flop changes state to gate the UNITED STATES PATENTS SCR into conduction. This time is made longer than the time 3,530,690 9/1970 Nickell etal 66/163 ofa p y of the loom 3,498,339 3/1970 Davis et al. 139/336 START l \(48 42 53 A P 56 I 1%25 47 36 5e 5| 4a 44 \i 39 a2 3a 23 Ar 40 ii 11 57 I e49 9 59$ A;

!45\ E 52 s i L f 1 TIME CYCLE WARP-STOP MOTION CONTROL FOR WEAVING LOOMS BACKGROUND OF THE INVENTION Prior art circuits are known for controlling the energization of a solenoid in a conventional knockoff stop control for looms. So far as we are aware, these circuits have always relied on a shipper handle switch to reset the circuits by the same motion of the shipper handle used to restart the loom on Fail- Safe, Power-Failure-Protected Systems. This requires very critical adjustment of the switch to allow time for the solenoid to energize and clear" the knockoff mechanism before the first pick. Any misadjustment of the switch results either in unnecessary shutdown of the loom or in a severe shock to the operator in holding the loom drive in engagement against the knockoff action. A prior circuit of this type is disclosed in the US. Pat. application Ser. No. 756,451, filed Aug. 30, 1968 now US. Pat. No. 3,498,337 and assigned to the same assignee as the present application SUMMARY OF THE INVENTION It is therefore a general object of the present invention to provide a solenoid control circuit for a knockoff stop system of a loom which overcomes the disadvantages of the prior art control circuits as described above;

It is a further object of this invention to provide a solenoid control circuit of this type in which reset of the circuit is independent of the control handle position and is automatically provided at the end of a time delay following the opening of the drop wire contacts.

It is a still further object of this invention to provide a solenoid control circuit of the above type in which the time delay is made longer than the pick-cycle time of the loom.

In attaining the objects of this invention, the circuit is powered directly from a low-voltage AC supply bypassing any shipper handle switch. Solenoid deenergization is controlled by the closing of drop wire contacts and is maintained for a time beyond the opening of said contacts by a timed-cycle circuit. Once a drop wire contact has caused deenergization of the solenoid, the latch-out will remain in effect for the duration of the drop wire contact plus a definite time delay longer than the loom pick cycle. Thus the solenoid will remain deenergized long enough to provide a controlled stop whether or not the drop wire remains in solid contact. Thus, after a controlled stop and after the broken warp threads have been repaired, the solenoid is already energized and the knockoff linkage is cleared before shipper handle engagement is attempted and without requiring any critical mechanical adjustment of a switch with respect to shipper handle movement.

DESCRIPTION OF THE INVENTION The single FIGURE of the drawing is a wiring diagram of the circuit of this invention applied to a conventional loomstop motion indicated schematically.

Referring now to the FIGURE, a conventional loom shipper handle which is shown in off position, may be moved in the direction of the arrow shown to start the loom for normal running. A loom shaft 11, provided with a cam 12 in conventional manner operates a knockoff mechanism, indicated schematically as 13, when the high point of cam I2 engages a push rod 14 to actuate rod 15 which knocks the shipper handle 10 to off position and shuts down the loom. The function of the knockoff mechanism 13, which is conventional, is to provide engagement or disengagement of the rods 14 and 15 responsively to the actuation of the armature 16 of solenoid 17 through a mechanical linkage 18. Thus, when the solenoid 17 is deenergized, the rods 14 and 15 are connected mechanically by actuation of linkage 18 so that motion imparted to rod 114 by cam 12 in a predetermined angular position of shaft 11 will move rod 15 to actuate the shipper handle 10 to off" position and shut down the loom. When, however, the solenoid 17 is energized, the linkage 18 moves to disconnect rod 14 from rod 15 and no motion is transmitted therebetween and the loom remains in operation. This type of solenoid-actuated knockoff mechanism is generally well known in the art and may, for example, be the same as that shown and described in the Sepavich et al. U.S. Pat. No. 2,436,022 and forms no part of this invention which is concerned with a circuit for controlling the energization of the solenoid 17. This circuit will now be described.

A source 8-8 of low AC voltage supplies voltage to lines 20-21. A silicon-controlled rectifier (SCR) 22 functions as a controlled switch has its anode 23 and cathode 24 connected in series with the solenoid l7 and a diode 25 across lines 20-21. The diode 25 is used in conventional manner to protect the SCR 22 from reverse anode voltages. A conventional freewheeling diode 26 shunts the solenoid l7 and provides a path for forward solenoid current during the time period between conducting positive half-cycles. When proper voltage is applied to the gate 27 of SCR 22 it conducts half-wave rectified AC through the solenoid 17. When this gate voltage is removed, the SCR 22 turns off by virtue of the zero voltage level at its anode 23 at the beginning of the next negative cycle in a well-known manner.

A diode 28, resistor 29 and capacitor 30 provide a DC voltage source at junction 31 for the gate 27 and the control circuitry. Transistors 32 and 33 and associated circuitry provide a high-hysteresis flip-flop which snaps" from one state to the opposite state responsive to highand low-limit threshold voltages developed at a control point 34 as will be described subsequently.

During periods when energization of solenoid 17 is required, transistor 32 is saturated and transistor 33 is cut ofi. Current for the gate 27 is then provided from junction 31 through resistors 35 and 36. Resistor 37 is a gate-to-cathode shunt provided for SCR stability as is well known.

For as long as transistor 32 remains saturated, all drive to the base 38 of transistor 33 is removed by the low impedance of the path between the collector 39 and emitter 40 of transistor 32 whereby transistor 33 is kept fully cut off. In this state, transistor 32 is kept saturated by current supplied to the base 41 from junction 31 by two paths. The first path through resistors 42, 43 and diode 44, with time delay afforded by capacitor 45, constitutes the timing control path. The second path, through resistors 35, 46 and diode 47, constitutes the latching path.

The switch 48 represents the drop wire contacts which are in common usage on looms to detect warp thread breakage. The function of switch 48 is to close responsively to warp breakage but obviously can be made to close responsively to any loom malfunction it is desired to detect. Thus, when switch 48 closes responsively to some loom malfunction, the AC voltage from 5-8 is applied to resistor 49. When the next negative half-cycle of voltage from S-S reaches a value sufficient to overcome the breakdown voltage of Zener diode 50 and the forward voltage drop in diode 51, discharge current rapidly flows out of capacitor 45 (which has previously been charged with the polarity shown) and discharges it. The diode 52 clamps the voltage at the control point 34 to eliminate large negative excursions thereof. An alternate to the discharge path through diode 51, Zener 50, resistance 58, and switch 48 could be accomplished by a discharge network consisting of a timing resistor in series with the drop wire switch. This network would then be connected directly between line 21 and junctions 34 or 60, as shown, for example, in dashed lines in the FIGURE.

When capacitor 45 has discharged to the extent that the voltage at the control point 34 falls below a lower threshold value of approximately 0.6 volts, both the timing path 42, 43 and 44, and the latching path 35, 46 and 47 (by virtue of flow through diode 53) are so severely shunted that all current is diverted from the base 41 and transistor 32 comes out of saturation. The voltage at collector 39 rises and applies base current drive to base 38 (limited only be resistor 54) thus bringing transistor 33 out of cutoff. As transistor 33 begins to conduct, the voltage at its collector 55 decreases further removing the latching current through resistor 46 and diode 47 to base 41.

At this point the flip-flop snaps to the reverse state, that is, with transistor 32 fully cut off and transistor 33 fully saturated. Thus in this state, with collector 55 at approximately volts, the current drive to the gate 27 is removed and the solenoid 17 is deenergized. The mechanism, now set for loom knockoff through linkage 18, causes loom shutdown the next time the high point of cam 12 actuates the rod 14 as is well understood For as long as switch 48 remains closed, capacitor 45 cannot charge and transistor 32 cannot conduct. When switch 48 opens, however, capacitor 45 begins to charge from current supplied from junction 31 through resistor 42. Thus the voltage at the control point 34 follows the capacitor voltage and, as soon as it reaches a sufficiently positive upper threshold level, transistor 32 begins to conduct causing transistor 33 to come out of saturation. Once the voltage at the collector 55 increases sufficiently, the latch-in current through resistor 46 and diode 47 to the base 41 is reapplied snapping the flip-flop into the state wherein transistor 32 is saturated and transistor 33 is cut off. The solenoid 17 will now be energized and is ready for the operator to start the loom.

Resistors 56 and 57 constitute a voltage divider for the voltage at 31 and provides a reference voltage at point 60 for comparison with the voltage at control point 34. Thus, whenever the voltage at junction 31 drops, as would occur during a momentary power failure, the capacitor 45 is provided with a quick discharge path through resistor 57 and the circuit behaves in the same manner as described above with respect to closure of switch 48. This guarantees a controlled stop even if power is suddenly reapplied. Resistor 58 limits the discharge current from capacitor 45 and resistor 59 controls the base bias of transistor 32.

From the above description, it will be apparent that the flipflop action of transistors 32 and 33 is responsive to two critical threshold values of the voltage at control point 34. Above a certain value, say 2.2 volts, at point 34, the solenoid will be energized and below a lower value, say 0.6 volts, at point 34, the solenoid will be deenergized. Between these two values, the solenoid can be either energized or deenergized depending on its previous condition. The voltage at point 34 can vary from substantially 0 volts (when capacitor 45 is discharged) to that voltage determined substantially by the voltage of junction 31 and the ratio of resistors 56 and 57 modified somewhat by diode and transistor junctions. By choice of circuit constants, rate of discharge of capacitor 45, initiated by closure of switch 48, can be made such that the time for the voltage at 34 to drop 0.6 volts can be very small in which case the solenoid 17 is deenergized substantially simultaneously with closure of switch 48. Similarly by choice of other circuit constants, the rate of charging of capacitor 45, initiated by opening of switch 48 can be made such that a definite predetermined time must elapse for the voltage at point 34 to rise from 0 to 2.2 volts, in which case the energization of the solenoid 17 takes place at a definite time delay after the opening of switch 48.

In a practical embodiment of this invention applied to a loom having a pick-cycle time of from 300 to 500 milliseconds, the time delay is set at 750 milliseconds which insures a controlled stop for any opening of the switch 48 and for even a momentary loss of power. Obviously, the time delay may be chosen, in any specific case, to be sufficiently longer than the pick-cycle time to attain the above-desired results in accordance with the teachings of this invention.

Having thus described the invention, it will be seen that changes and modifications may be made therein by those skilled in the art without departing from the spirit and scope of the invention and no limitation thereof is intended with respect to the details disclosed.

Having thus set forth the nature of this invention, what we claim herein is:

1. In a stop system for a loom having a knockoff device rendered effective responsively to deenergization of a solenoid to cause the shipper handle to sto the loom at a predetermined point in its operating cycle w en actuated by a cyclically moving part of the loom, a circuit for controlling the energization of the solenoid from a voltage source comprising:

a. a controlled switch,

b. means connecting said controlled switch in series with said solenoid and with said voltage source,

c. means applying a signal to said controlled switch sufficient to cause it normally to conduct and energize said solenoid,

d. switch means actuated to a first position responsive to a loom malfunction for removing said gating signal and deenergizing said solenoid,

e. means operative responsively to actuation of said switch means from its first to its second position upon removal of said malfunction to initiate the reapplication of said gating signal to said controlled switch, and means for delaying the reapplication of said gating signal to said controlled switch, for a definite time following the initiation thereof, said definite time being related to the time period of a loom operating cycle.

A circuit according to claim 1 wherein:

a flip-flop having two stable states controls respectively the application and removal of said gating signal to and from said controlled switch, and

b. a capacitor, charged and discharged at controlled rates by actuation of said switch means, determines the state of the flip-flop.

3. in a stop system for a loom having a knockoff device rendered effective responsively to deenergization of a solenoid to cause the shipper handle to stop the loom at a predetermined point in its operating cycle when actuated by a cyclically moving part of the loom, a circuit for controlling the energization of the solenoid from an AC voltage source comprising:

a. a controlled rectifier,

b. means connecting said rectifier in series with said solenoid and with said AC voltage source,

c. a flip-flop having two stable states controlling respectively the application and removal of a DC conduction gating signal to and from the controlled rectifier,

a capacitor,

means for charging and discharging said capacitor,

nonnally open switch means actuated to closed position responsive to loom malfunction,

g. means responsive to the closing and opening of said switch means for initiating respectively the discharging and charging of said capacitor,

. means responsive to the voltage across said capacitor for causing the flip-flop to change state, and

. means for controlling the charging time of said capacitor so that the time required to change the state of the flip flop in one direction is longer than the period of one operating cycle of the loom.

4. A circuit for controlling the energization of a solenoid according to claim 1 wherein said controlled switch is a solidstate semiconductor device.

5. A circuit for controlling the energization of a solenoid according to claim 4 wherein said solid-state semiconductor device is a controlled rectifier.

6. A circuit for controlling the energization of a solenoid according to claim 1 wherein said voltage source is a relatively low AC voltage source.

7. A circuit for controlling the energization of a solenoid according to claim 1 wherein said switch means in said first position is closed and in said second position is open. 

1. In a stop system for a loom having a knockoff device rendered effective responsively to deenergization of a solenoid to cause the shipper handle to stop the loom at a predetermined point in its operating cycle when actuated by a cyclically moving part of the loom, a circuit for controlling the energization of the solenoid from a voltage source comprising: a. a controlled switch, b. means connecting said controlled switch in series with said solenoid and with said voltage source, c. means applying a signal to said controlled switch sufficient to cause it normally to conduct and energize said solenoid, d. switch means actuated to a first position responsive to a loom malfunction for removing said gating signal and deenergizing said solenoid, e. means operative responsively to actuation of said switch means from its first to its second position upon removal of said malfunction to initiate the reapplication of said gating signal to said controlled switch, and f. means for delaying the reapplication of said gating signal to said controlled switch, for a definite time following the initiation thereof, said definite time being related to the time period of a loom operating cycle.
 2. A circuit according to claim 1 wherein: a. a flip-flop having two stable states controls respectively the application and removal of said gating signal to and from said controlled switch, and b. a capacitor, charged and discharged at controlled rates by actuation of said switch means, determines the state of the flip-flop.
 3. In a stop system for a loom having a knockoff device rendered effective responsively to deenergization of a solenoid to cause the shipper handle to stop the loom at a predetermined point in its operating cycle when actuated by a cyclically moving part of the loom, a circuit for controlling the energization of the solenoid from an AC voltage source comPrising: a. a controlled rectifier, b. means connecting said rectifier in series with said solenoid and with said AC voltage source, c. a flip-flop having two stable states controlling respectively the application and removal of a DC conduction gating signal to and from the controlled rectifier, d. a capacitor, e. means for charging and discharging said capacitor, f. normally open switch means actuated to closed position responsive to loom malfunction, g. means responsive to the closing and opening of said switch means for initiating respectively the discharging and charging of said capacitor, h. means responsive to the voltage across said capacitor for causing the flip-flop to change state, and i. means for controlling the charging time of said capacitor so that the time required to change the state of the flip-flop in one direction is longer than the period of one operating cycle of the loom.
 4. A circuit for controlling the energization of a solenoid according to claim 1 wherein said controlled switch is a solid-state semiconductor device.
 5. A circuit for controlling the energization of a solenoid according to claim 4 wherein said solid-state semiconductor device is a controlled rectifier.
 6. A circuit for controlling the energization of a solenoid according to claim 1 wherein said voltage source is a relatively low AC voltage source.
 7. A circuit for controlling the energization of a solenoid according to claim 1 wherein said switch means in said first position is closed and in said second position is open. 